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'PIC16F84 COM84 programming again...'
1997\02\25@183945 by Tapani T. Salmi

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Does someone know the common problems & solutions for the COM84
programmer? My attempts to program PIC16F84 with COM84 has been
very unsuccesful.

I build my COM84 with instructions found from
http://hobbes.king.ac.uk/matt/pic/prog.html. Is that circuit ok? When I
write something with pip02 program (I use com84.exe driver, does it work
with 16F84) I get programming error. Reading the chip always tells me 3f
ff stuff.

Even that the circuit is very simple, I tried it again: I asked my friend
to make the COM84, we used a fresh PIC and his computer. Nada, same
symptoms.

But I think that there is something strange going on, because while
programming, my multimeter shows only about 5-6V as the voltage of MCLR.
As far as I know, it can't be right? It should be higher? Is the problem
too low voltage, possibly caused by lame serial ports? (but if it's so,
lame RS ports are very common; I have tried two different mother board
integrated and one separate adapter card) Or is MCLR switched on/off
during write procedure?

Please, can you tell me what is going wrong?

/Taiska (novadays known as Desperado :(

1997\02\25@185037 by Antti Lukats

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At 01:37 AM 26/2/97 +0200, you wrote:
>Does someone know the common problems & solutions for the COM84
>programmer? My attempts to program PIC16F84 with COM84 has been
>very unsuccesful.
>
>I build my COM84 with instructions found from
>http://hobbes.king.ac.uk/matt/pic/prog.html. Is that circuit ok? When I
>write something with pip02 program (I use com84.exe driver, does it work
>with 16F84) I get programming error. Reading the chip always tells me 3f
>ff stuff.
>
>Even that the circuit is very simple, I tried it again: I asked my friend
>to make the COM84, we used a fresh PIC and his computer. Nada, same
>symptoms.
>
>But I think that there is something strange going on, because while
>programming, my multimeter shows only about 5-6V as the voltage of MCLR.

this is the problem, unless the voltage is >= 10.5 the programmer will not
program or read any chips.
I suggest you make a simple LPT programmer. PIP02 now supports NOPPP
almost simpliest LPT programmer.

>As far as I know, it can't be right? It should be higher? Is the problem
>too low voltage, possibly caused by lame serial ports? (but if it's so,
>lame RS ports are very common; I have tried two different mother board
>integrated and one separate adapter card) Or is MCLR switched on/off
>during write procedure?
>
>Please, can you tell me what is going wrong?

maybe you use 7805 on your programmer? it takes too much current
78L05 or zener can be used.

antti

The COM84 hardware or whatever a-like is not our design, we only wrote
a driver for our programming software.

-- Silicon Studio Ltd.
-- http://www.sistudio.com

1997\02\25@190522 by Tapani T. Salmi

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On Tue, 25 Feb 1997, Antti Lukats wrote:

> >But I think that there is something strange going on, because while
> >programming, my multimeter shows only about 5-6V as the voltage of MCLR.
>
> this is the problem, unless the voltage is >= 10.5 the programmer will not
> program or read any chips.

Yeah, so I guessed it. Thanks.

> maybe you use 7805 on your programmer? it takes too much current
> 78L05 or zener can be used.

Regulator says LM78L05ACZ, so it is ok? Anyway, LPT programmers sounds
good idea. Maybe I can get it working...

/Taiska

1997\02\26@011446 by Dennis Frost

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Hi Taiska     (Alias Desperado)

Here is a diagram of the changes I made to the Com84 programmer. I have
been using it for a year on a 120 Meg Pentium without problems. (If you
can't make out the circuit then cut it out & paste it into notebook)
I like this programmer because I usually have other things plugged into my
parallel ports.

Don't give up hope. I started in Pics trying to use a Parallel programmer
and had all sorts of problems. That's why I now use a serial programmer.
How can you get simpler than 3 resistors?


Cable to PC's     :       Unit under development
  serial port     :
                  :    +--------+---> 5V from on board PSU
                  :    |        |
                  :    |        |
                  :    /        |
                  :    \10K     |
                  :    /        |
                  :    \        |
                  :    |        |14
                  :    |  +-----------+
                  :    |  |     Vdd   |
                  :    |  |           |
  3   1K     /    :    | 4| ____      |
TXD---/\/\/--o  o--:----+--| MCLR      |-------
           switch :       |           |
                  :       |           |-------
                  :       |  16C84    |
                  :       |    or     |-------
                  :       |  16F84    |
                  :       |           |-------
                  :       |           |
  7   2K2         :     12|           |-------
RTS---/\/\/--------:-------|RB6        |
                  :       |           |
  4   2K2         :     13|           |
DTR---/\/\/--+-----:-------|RB7        |
  8         |     :       |           |
CTS----------+     :       |    Vss    |
                  :       +-----------+
                  :             |5
                  :             |
  5               :             |
GND----------------:-------------+---> 0V from on board PSU
                  :

PIP02 works very well but be careful. V1.14 has some bugs. One is that the
configuration bits
are not picked up from your hex file correctly and the other is you cannot
compile in MPLAB (Under windows) if you have PIP02 V1.14 open in another
window. PIP02 doesn't close the hex file so MPLAB cannot access it. This
wasn't the case with the older version.


----------
{Quote hidden}

1997\02\26@150328 by Leon Heller

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In message <Pine.LNX.3.95.970226011247.28240C-100000spamKILLspammorgoth.tuug.org>,> "Tapani T. Salmi" <.....taiskaKILLspamspam.....TUUG.ORG> writes
{Quote hidden}

Serial ports do seem to vary a lot. I have the same problem with my new
P133+ system with the I/O on the M/B, whereas my old 486 system with a
simple I/O card works fine, as does my 486 system at work. I'd try
adding the 555 voltage doubler circuit. I'll be trying this myself.

Leon
--
Leon Heller, G1HSM
EraseMEleonspam_OUTspamTakeThisOuTlfheller.demon.co.uk
Tel: +44 (0) 118 947 1424 (home)
    +44 (0) 1344 385556 (work)


'PIC16F84 COM84 programming again...'
1997\03\05@154106 by peter
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Tapani T. Salmi wrote:
{Quote hidden}

Try putting 18pf caps on RB6 and RB7 and/or clock in (LPT pin 3)
and data (LPT pin 2)

I had the same problem and the caps fixed it
--
Peter Cousens
email: peterspamspam_OUTcousens.her.forthnet.gr
snailmail: Peter Cousens, karteros, Heraklion, Crete, 75100, Greece,
phone: + 3081 380534,    +3081 324450   voice/fax

After Bill Gates announced to the world that he was Microsoft,
his wife was asked to comment. She said that as his wife, she
had been the first to notice this problem

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